Applicants claim priority under 35 U.S.C. xc2xa7119 of GERMAN Application No. 100 20 884.3 filed on Apr. 28, 2000. Applicants also claim priority under 35 U.S.C. xc2xa7365 of PCT/DE01/01532 filed on Apr. 20, 2001. The international application under PCT article 21(2)was not published in English.
The invention relates to a control device for an intake or exhaust valve of an internal combustion engine according to the preamble of patent claim 1.
For control devices with the characteristics a to f of the preamble of claim 1, various valve controls can be switched in relation to varying loads or motor brake operation for example. Such devices of the most diverse embodiments are known, for example, from DE 27 53 197 A1, DE 36 13 945 A1, DE 38 00 347 A1, DE 41 36 143 A1, EP 0 775 251 B1, U.S. Pat. No. 5,544,626 and JP 6-88 512 A.
With all these devices where the control element is a cam shaft, the different contours of the control cams on the cam shaft have to fall inside each other, i.e. within an envelope curve which is determined by the control curve of the control cam with the greatest sweep. Otherwise, these known devices cannot operate. In systems such as EP 0 458 857 B1 for example, a switch between different control contours occurs such that in a control state with play, a standard control contour is achieved. In a further control state, the entire cam profile for the valve motion available on the cam shaft is activated by removing the play. The additional control contour is engaged while the standard contour in such a system cannot be disengaged. The control contour is proportional to the entire envelope curve of the cam shaft. To the extent that, for the control device according to EP 0 775 251 B1, a valve control predetermined by the control curve of the control cam can be varied in conjunction with a hydraulic unit, not just any desired valve controls can be achieved. Neither can the stroke of the standard motion be disengaged.
Similar control devices with similar disadvantages and sometimes with particularly complex design features are also known from DE 32 19 611 A1, FR 27 09 150 A1, FR 27 09 149 A1, U.S. Pat. No. 5,564,373, JP 55-152308 U and from JP Patent Abstracts of Japan: 10077815 A, 07317081 A, 07077109 A, 03179115 A, 02252910 A as well as 02095708 A.
The genre-forming state of the art, from which the preamble of patent claim 1 has been derived, is xe2x80x9cMULTI-MODE VARIABLE VALVE TIMING ENGINExe2x80x9d, AUTOMOTIVE ENGINEERING, SOCIETY Of AUTOMOTIVE ENGINEERS. WARRENDALE, US, VOL. 102, No. 2, PAGE(S) 111-114 XP000426931 ISSN: 0098-2571.
In a generically appropriate device, the invention deals with the problem of enabling a simple and reliable switching of KEB areas, being in a state of force transmission, between control element and valve.
This problem is solved by the design of a generically appropriate control device according to the characteristic features of claim 1.
In the above-mentioned, genre-forming, known device, the KEB areas are in constant contact with the correlated control curve areas of the control element whereby only the KEB area not transmitting any force is held, without being locked, in the base body of the adjustment element such that it can follow the control curve without acting in a force-transmitting way. The required locking of that KEB area being switched to force transmission at the time, takes place not hydraulically but mechanically with the engagement of a pin in the movably mounted part of the KEB area. Only the pin is moved hydraulically, but its locking force is based on mechanical engagement rather than hydraulic forces. Due to the mechanical locking technique for the KEB areas, employed for this known device, switching is only possible for states of motion where the pin and the locking hole correlated to it are in line with each other which in practice is only possible when the relevant KEB area to be switched is correlated with the base circle areas of the control curve of the cam shaft. Otherwise, a locking between the component containing the KEB area and the base body of the adjustment element is virtually impossible.
The invention according to claim 1 differentiates itself by the features g, h, i, j and k from the device according to U.S. Pat. No. 4,726,332. The essential difference can especially be found in the fact that for those devices, a control curve area of the cam shaft can only be disengaged if control curves are used which are not contained within the envelope curve of the above-mentioned control curve. This is a serious disadvantage compared to the teaching according to the invention so that said known device does not solve the problem in terms of the invention.
The same applies in relation to the device according to U.S. Pat. No. 5,042,437, where there is always a KEB area, too, which cannot be disengaged from a correlated control curve of the control shaft.
Advantageous and useful embodiments of the invention are the subject of the dependent claims.
If, between control elements with differing control curves and the valve to be controlled, an adjusting element is introduced whose points of engagement with the control curves and the valve can be infinitely adjusted relative to each other as desired, any desired, differing correlation to each other can be set. That way, any control settings can be achieved in a simple manner. As a control element, a cam shaft with differing control curves can be used or several cam shafts with differing control curves each can also be used. When using several cam shafts as a control element, the variability of the possible control settings is increased. Thus, especially cam shafts rotating at different speeds can be used.
Hydraulic units are used as switching means. The use of hydraulic units has the advantage that the moment transfer ranges of the adjusting element relative to the control element, on the one hand, and/or the valve, on the other hand, can be integrated. Thus, the valve play compensation measures, basically known for engine valve controls, can be integrated easily into these hydraulic units.
Advantageously, drag levers or rocker arms can be used as adjusting elements. It is also possible to use an adjusting element capable of linear motion only. Preferably, the force transfer takes place at the end of a valve stem or, if several valves are being operated, onto an intermediate element such as a valve bridge.